Quilting is a sewing process by which layers of textile material and other fabric are joined to produce compressible panels that are both decorative and functional. Stitch patterns are used to decorate the panels with sewn designs while the stitches themselves join the various layers of material that make up the quilts. The manufacture of mattress covers involves the application of large scale quilting processes. The large scale quilting processes usually use high-speed multi-needle quilting machines to form series of mattress cover panels along webs of the multiple-layered materials. These large scale quilting processes typically use chain-stitch sewing heads which produce resilient stitch chains that can be supplied by large spools of thread. Some such machines can be run at up to 1500 or more stitches per minute and drive one or more rows of needles each to simultaneously stitch patterns across webs that are ninety inches or more in width. Higher speeds, greater pattern flexibility and increased operating efficiency are constant goals for the quilting processes used in the bedding industry.
Conventional multi-needle quilting machines have three axes of motion. An X-axis can be considered as the longitudinal direction of motion of a web of the material as it moves through the quilting station. Frequently, such bi-directional motion is provided in which the web of material can move in either a forward or a reverse direction to facilitate sewing in any direction, such as is needed for the quilting of 360 degrees patterns on the material. Material accumulators usually accompany such bi-directional machines so that sections of a web can be reversed without changing the direction of the entire length of web material along the quilting line. A Y-axis of motion is also provided by moving the web from side to side, also for forming quilted patterns. Usually the quilting mechanism remains stationary in the quilting process and the motion of the material is controlled to affect the quilting of various patterns.
The X-axis and the Y-axis are parallel to the plane of the material being quilted, which traditionally is a horizontal plane. A third axis, a Z-axis, is perpendicular to the plane of the material and defines the nominal direction of motion of reciprocating needles that form the quilting stitches. The needles, typically on an upper sewing head above the plane of the material, cooperate with loopers on the opposite or lower side of the material, which reciprocate perpendicular to the Z-axis, typically in the X-axis direction. The upper portion of the sewing mechanism that includes the needle drive is, in a conventional multi-needle quilting machine, carried by a large stationary bridge. The lower portion of the sewing mechanism that includes the looper drives is attached to a cast iron table. There may be, for example, three rows of sewing elements attached to each respective upper and lower structure. All of the needles are commonly linked to and driven by a single main shaft.
Conventional multi-needle quilting machines use a single large presser foot plate that compresses the entire web section of material in the sewing area across the width of the web. On a typical machine that is used in the mattress industry, this presser foot plate might, during each stitch, compress an area of material that is over 800 square inches in size to a thickness of as little as ¼ inch. When the needles are withdrawn from the material following each stitch formation, the presser foot plate must still compress the material to about 7/16 inch. Since the material must, while still under the presser foot plate, move relative to the stitching elements to form the pattern, patterns are typically distorted by the drag forces exerted on it parallel to the plane of the material. These conventional machines are large and heavy, and occupy a substantial area on the floor of a bedding manufacturing plant.
Further, multi-needle quilting machines lack flexibility. Most provide a line or an array of fixed needles that operate simultaneously to sew the same pattern and identical series of stitches. Changing the pattern requires the physical setting, rearrangement or removal of needles and the threading of the altered arrangement of needles. Such reconfiguration takes operator time and substantial machine down-time.
Traditional chain stitch machines used for quilting reciprocate one or more needles through thick multi-layered material using a crank mechanism driven by a rotary shaft. The force of a drive motor, as well as inertia of the linkage, forces the needle through the material. The needle motion so produced is traditionally sinusoidal, that is, it is defined by a curve represented by the equation y=sine x. For purposes of this application, motion that does not satisfy that equation will be characterized as nonsinusoidal. Thus, the needle motion carries a needle tip from a raised position of, for example, one inch above the material, downward through material compressed to approximately ¼ inch, to a point about ½ inch below the material where its motion reverses. The needle carries a needle thread through the material and presents a loop on the looper side of the material to be picked up by a looper thread. On the looper side of a material, a looper or hook is reciprocated about a shaft in a sinusoidal rotary motion. The looper is positioned relative to the needle such that its tip enters the needle thread loop presented by the needle to extend a loop of looper thread through the needle thread loop on the looper side of the material. The motion of the looper is synchronized with motion of the needle so that the needle thread loop is picked up by the looper thread when the needle is at the downward extent of its cycle. The needle then rises and withdraws from the material and leaves the needle thread extending around the looper and looper thread loop.
When the needle is withdrawn from the material, the material is shifted relative to the stitching elements and the needle again descends through the material at a distance equal to one stitch length from the previous point of needle penetration, forming one stitch. When again through the material, the needle inserts the next loop of needle thread through a loop formed in the looper thread that was previously poked by the looper through the previous needle thread loop. At this point in the cycle, the looper itself has already withdraw from the needle thread loop, in its sinusoidal reciprocating motion, leaving the looper thread loop extending around a stitch assisting element, known as a retainer in many machines, which holds the looper thread loop open for the next decent of a needle. In this process, needle thread loops are formed and passed through looper thread loops as looper thread loops are alternatively formed and passed through needle thread loops, thereby producing a chain of loops of alternating needle and looper thread along the looper side of the material, leaving a series of stitches formed only of the needle thread visible on the needle side of the material.
The traditional sinusoidal motion of the needle and looper in a chain stitch forming machine have, through years of experience, been adjusted to maintain reliable loop-taking by the thread so that stitches are not missed in the sewing process. In high speed quilting machines, the motion of the needle is such that the needle tip is present below the plane of the material, or a needle plate that supports the material, for approximately ⅓ of the cycle of the needle, or 120 degrees of the needle cycle.
During the portion of the needle cycle when the needle extends through the material, no motion of the material relative to the needle is preferred. Inertia of machine components and material causes some of the between-stitch motion of material relative to the needle to occur with the needle through the material. This results in needle deflection, which can cause missed stitches as the looper misses a needle thread loop or the needle misses a looper thread loop, or causes loss of pattern definition as material stretches and distorts. Further, limiting the time of needle penetration of the fabric defines the speed of the needle through the fabric, which determines the ability of the needle to penetrate thick multi-layered material. Increase of the needle speed then requires increasing the distance of needle travel, which causes excess needle thread slack below the fabric that must be pulled up to tighten the stitches during the formation of the stitches. Accordingly, the traditional needle motion has imposed limitations on chain stitch sewing and particularly on high speed quilting.
Further, looper heads on known multi-needle quilting machines provide the looper motion by moving cam followers over a cam surface, which requires lubrication and creates a wear component requiring maintenance.
Additionally, chain stitch forming elements used on multi-needle quilting machines typically each include a needle that reciprocates through the material from the facing side thereof and a looper or hook that oscillates in a path on the back side of the material through top-thread loops formed on the back side of the material by the penetrating needle. Chain stitching involves the forming of a cascading series or chain of alternating interlocking between a top thread and a bottom thread on the back side of the material by the interaction of the needle and looper on the backside of the material, which simultaneously forms a clean series of top-thread stitches on the top side of the material. The reliable forming of the series of stitches requires that the paths of the needle and looper of each stitching element set be accurately established, so that neither the needle nor the looper misses the take-up of the loop of the opposing thread. The missing of such a loop produces a missed stitch, which is a defect in the stitching pattern.
Initially, and periodically in the course of the use of a quilting machine, the relative positions of the needle and the looper must be adjusted. Typically, this involves the adjusting of the transverse adjustment of the position of the looper on its axis of oscillation. In multi-needle quilting machines, such an adjustment is made to bring the path of the looper in close proximity to the side of the needle just above the eye in the needle through which is passed the top thread. At this position, a loop of the needle thread is formed beside the needle through which the looper tip inserts a loop of the bottom thread. The formations of these loops and the interlocking chain of stitches is described in detail in U.S. Pat. No. 5,154,130, hereby expressly incorporated herein by reference.
Looper adjustment has been typically a manual process. The adjustment is made with the machine shut down by a technician using some sort of a hand tool to loosen, reposition, check and tighten the looper so that it passes close to or lightly against the needle when the needle is near the bottom-most point in the needle's path of travel on the bottom side of the material being quilted. The adjustment takes a certain amount of operator time. In a multi-needle quilting machine, the number of needles may be many, and the adjustment time may be large. It is not uncommon that the quilting line would be shut down for the major portion of an hour or more just for needle adjustment.
Furthermore, since the looper adjustment has been a manual process, difficulties of access to the adjusting elements, difficulties in determining the relative looper and needle positions, and difficulties in holding the adjusting elements in position while securing or locking the locking components of the assemblies has served as a source of adjustment error.
Chain stitch forming elements used on multi-needle quilting machines typically each include a needle that reciprocates through the material from the facing side thereof and a looper or hook that oscillates in a path on the back side of the material through top-thread loops formed on the back side of the material by the penetrating needle. Chain stitching involves the forming of a cascading series or chain of alternating interlocking between a top thread and a bottom thread on the back side of the material by the interaction of the needle and looper on the backside of the material, which simultaneously forms a clean series of top-thread stitches on the top side of the material. The top thread or needle thread penetrates the fabric from the top side or facing side of the fabric and forms loops on the bottom side or back side of the fabric. The bottom thread remains exclusively on the back side of the fabric where it forms a chain of alternating interlocking loops with the loops of the top thread.
High speed multi-needle quilting machines, such as those that are used in the manufacture of mattress covers, often sew patterns in disconnected series of pattern components. In such sewing, tack stitches are made and, at the end of the quilting of a pattern component, at least the top thread is cut. Then the fabric advances relative to the needles to the beginning of a new pattern component, where more tack stitches are made and sewing recommences. One such high speed multi-needle quilting machine is described in U.S. Pat. No. 5,154,130, referred to above. This patent particularly describes in detail one method of cutting thread in such multi-needle quilting machines. Accordingly, there is a need for more reliable and more efficient thread management in multi-needle quilting machines.
These characteristics and requirements of high-speed multi-needle quilting machines, and the deficiencies discussed above, impede the achievement of higher speeds and greater pattern flexibility in conventional quilting machines. Accordingly, there is a need to overcome these obstacles and to increase the operating efficiency of quilting processes, particularly for the high volume quilting used in the bedding industry.